Abstract
Blaberus discoidalis hypertrehalosemic hormone (HTH= PQVNFSPGWGT-NH2) is a member of the AKH/RPCH family of insect neuropeptides and stimulates fat body trehalose synthesis. A series of Nterminal fragment standards of HTH were used for the development of an HPLC method for monitoring the breakdown products of HTH in hemolymph samples and in vitro incubation medium. Examination of [3H-pQl]HTH by HPLC indicated that the breakdown products of HTH relative to the pQ were: PQVNFSPG-OH (HTH 1-7), PQVNFS-OH (HTH 1-5), and PQVNF-OH (HTH 1-4). HTH 1-7 was present at more than lOx the concentration of the other two metabolic products indicating that this was a major endopeptidase cleavage site. At pharmacological HTH concentrations (200 jiM) the primary degradation product appeared to be a cleavage between Phe4 and Ser5. it is possible that more than one enzyme might be involved in HTH degradation. In order to determine if there is more than one enzyme, analogs beyond the scope if this study would need to be designed and analyzed. dYl-HTH (Ac-dYVNFSPGWGT-NH2), an analog of HTH, was cleaved between Asn3 and Phe4. This cleavage site was indicative of an endopeptidase 24.11-like cleavage, but was not inhibited by phosphoramidon, a specific EP 24.11 inhibitor. HTH degradation was also analyzed by matrix-assisted laser desorption and ionization mass spectrometry (MALDI-MS). MALDI-MS was shown to be a good alternative to HPLC based on the sensitivity, reproducibility, and reduced analysis time.
Strey, Allison Andrews (1994). Biodegration of hypertrehalosemic hormone in the cockroach Blaberus discoidalis. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -S915.